Differential Diagnosis of Behavioral Variant and Semantic Variant of Frontotemporal Dementia Using Visual Rating Scales.

Background: Frontotemporal dementia (FTD) represents the second most frequent early onset of dementia in people younger than 65 years. The main syndromes encompassed by the term FTD are behavioral variant of Frontotemporal dementia (bvFTD), non-fluent variant primary progressive aphasia (nfvPPA) and semantic variant (SD).

Aims: To assess the bvFTD and SD, which represent the most common subtypes of FTD, using visual rating scales.

Methods: Brain MRI exams of 77 patients either with bvFTD (n=43) or SD (n=34) were evaluated. The rating scales used were: Global cortical atrophy (GCA), Fazekas Scale: periventricular (PV) and white matter (WM) changes, Koedam rating scale and visual scales regarding specific cortical regions: dorsofrontal (DF), orbitofrontal (OF), anterior cingulate (AC), basal ganglia (BG), anterior- temporal (AT), insula, lateral-temporal (LT), entorhinal (ERC), perirhinal (PRC), anterior fusiform( AF), anterior hippocampus (AHIP) and posterior hippocampus (PHIP). Both Left (L) and Right (R) hemispheres were evaluated.

Results: R-OF (p=0.059), L-OF (p<0.0005), L-AT (p=0.047) and L-AHIP (p=0.007) have a statistically significant effect on the variable occurrence of SD compared to bvFTD. The indicators with the highest value of the area under the curve (AUC) were R-AC (0.829), L-OF (0.808), L-AC (0.791) and L-AF (0.778). Highest sensitivity was achieved by R-OF (97%) and L-AF (75%). Highest specificity was achieved by L-OF (95%), L-AT (91%) followed by R-AC (84%). Best combination of sensitivity and specificity was achieved by L-AF (74%-79%), L-OF (56%-95%) and R-OF (97%-42%). Best combination of PPV and NPV was achieved by L-OF (90%-73%), LAT (83%-72%) and R-AC (77%-77%).

Conclusion: Visual rating scales can be a practical diagnostic tool in the characterization of patterns of atrophy in FTLD and may be used as an alternative to highly technical methods of quantification.